The present invention is related to the field of semiconductor fabrication and more particularly to a process of forming interlevel dielectric materials with reduced water adsorption to improve subsequent metalization processes.
In the field of semiconductor fabrication, the desorption of water vapor from the wafer surface prior to metal deposition plays a key role in metal deposition processes. More particularly, water vapor from interlevel dielectric (ILD) layers can be incorporated into subsequently deposited films, such as tantalum (Ta), copper (Cu), aluminum (Al), and other metallic films, thereby altering their characteristics. If the desorption of water is significant, the resistivity of the subsequently deposited metal layer can be adversely affected through a water vapor initiated oxidation process. In addition, the desorption of water vapor from the ILD layer can result in undesirable particle formation during the deposition of a barrier layer in the metalization process.
In the field of semiconductor fabrication, it is becoming increasingly desirable to implement interlevel dielectric materials having a low dielectric constant (low k). For the purposes of this specification, a low dielectric constant material is a material having a dielectric constant less than that of silicon dioxide (k less than approximately 3.8). Low k dielectric materials reduce the coupling capacitance within a given metal layer and between adjacent metal layers, thereby increasing device speed. In one implementation, a low k dielectric material is achieved by incorporating fluorine into a dielectric material such as silicon dioxide (SiO2). However, the fluorinated oxide films tend to adsorb water more readily than unfluorinated films. The adsorption of water in the fluorinated oxide film can negatively impact a subsequent metalization process by increasing the resistivity of the resulting metal and by producing contamination in the metalization chamber. Therefore, it would be desirable to implement an ILD process that produces a low k dielectric layer exhibiting low water vapor adsorption characteristics. It would be further desirable if the implemented process did not significantly increase the cost or complexity of the fabrication process and did not significantly alter the characteristics of the ILD material.